Process of making a pressure-sensitive adhesive material

ABSTRACT

A PRESSURE SENSITIVE ADHESIVE MATERIAL IS MADE BY COATING A SUBSTRATE WITH A COPOLYMER OF SPECIFIED PROPORTIONS OF A DIESTER OF FUMARIC ACID, AND A VINYL COMPOUND COPOLYMERISABLE THEREWITH AS WELL AS EITHER OR BOTH OF AN OLEFINICALLY UNSATURATED COPOLYMERISABLE POLAR COMPOUND WITH CARBOXYL, CARBOXAMIDE, DICARBOXYLIC ANHYDRIDE OR DICARBOXYIMIDE GROUPS, AND AN OLEFINICALLY UNSATURATED COPOLYMERISABLE COMPOUND WITH SELF-CROSS-LINKABLE REACTIVE GROUPS, TOGETHER WITH A CROSS-LINKING POLYFUNCTIONAL COMPOUND, AND SUBJECTING THE COATING THEREON TO A SHORT PERIOD HEAT TREATMENT.

United States Patent 3,690,937 PROCESS OF MAKING A PRESSURE-SENSITIVE ADHESIVE MATERIAL Gunter Guse and Hanns G. Pietsch, Hamburg, Germany,

assignors to Beiersdorf Aktiengesellschaft, Hamburg,

Germany No Drawing. Filed Aug. 3, 1970., Ser. No. 60,629 Claims priority, application Germany, Aug. 8, 1969,

P 19 40 549.3 Int. Cl. C09j 7/02 US. Cl. 117-122 P 11 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a process for the manufacture of self adhesive tapes or fails having an adhesive which will adhere on pressure on the basis of copolymers of diesters of fumaric acid and vinyl compounds copolymerisable therewith.

It is known to use homoor co-polymers of acrylic acid esters or copolymers of acrylic acid esters with other unsaturated monomers polymerisable therewith as pressuresensitive adhesives for making self-adhesive materials of various types. Furthermore, pressure-sensitive adhesive coatings have been described of a copolymer resulting from copolymerisation of one or more acrylic acid esters with a small amount of a diester of fumaric acid, which contained 4 to 6 carbon atoms in the alcohol residue. The addition of the fumaric ester serves in this case to facilitate the temperature control during polymerisation and to reduce the cost of the end product. It also serves to modify the properties of the copolymer, e.g. for internal plasticisation. Such self-adhesive tapes or foils do not, however, come up to the elevated requirements which are required of them with respect to their adhesive power and cohesiveness, especially when they are destined for packing machinery.

A process for the manufacture of copolymers containing N-vinylpyrrolidone is also known, by the polymerisation of N-vinylpyrrolidones with esters of unsaturated dicarboxylic acids, wherein the molar ratio of N- vinylpyrrolidone to dicarboxylic acid ester is from 1 to :1. As dicarboxylic acid ester there may be used, forexample, dialkyl maleates and substituted dialkyl maleates or dialkyl fumarates. The resulting copolymers can be used as adhesives for laminating foils of polyethylene, polyethyleneglycolterephthalate, vinyl chloride/vinylidene chloride copolymers, aluminium foils, waxor kraft paper either to themselves or to others of the materials noted.

A copolymer made using di-Z-ethylhexyl maleate and N-vinyl-2-pyrrolidone can be used to make a pressure sensitive hydrated cellulose adhesive tape, but such adhesive tapes do not have adhesive and cohesive properties suflicient for self-adhesive foils.

Finally, it is known to make a permanently tacky copolymer by polymerisation of 100 parts by weight of a 3,690,937 Patented Sept. 12, 1972 monomer mixture of 3040 parts by weight vinyl acetate and correspondingly 67-70 parts by weight of a monoalkyl ester of an a, B ethylenically unsaturated monocarboxylic acid or a dialkyl ester of an a, p ethylenically unsaturated dicarboxylic acid or mixtures of monoalkylesters and dialkylesters. There can be used for monoalkyl este'rs oz, 5 unsaturated monocarboxylic acids with 3 to 5 carbon atoms, such as acrylic acid, methacrylic acid and crotonic acid, as for dialkyl esters, a, [3 unsaturated dicarboxylic acids with 4 to 5 carbon atoms, such as maleic acid, fumaric acid and itaconic acid. Each alkyl portion of the ester group should contain 7 to 12 carbon atoms.

The copolymers produced by this known process serve as permanently tacky adhesives, preferably in the form of a latex emulsion, for sticking difiiculty adherable surfaces of polymers, such as of polyethylene, polypropylene and other highly hydrophobic polymers, to the same surfaces or to other material. For this, the adhesive in the adhesive join between the two stuck together surfaces should have a permanent tack.

The preferred application of these known copolymers thus lies in the area of permanent adhesion of large fabric surfaces (lamination of foils). Similarly, the known copolymers also find employment as pressure sensitive adhesives and separating coats. The known copolymers, however, do not constitute useable pressure sensitive adhesives for the manufacture of self adhesive tapes or foils, which as well as having a high adhesive power, have to have at the same time a suflicient internal strength.

The object of the invention is the manufacture of selfadhesive tapes or foils with a pressure sensitive adhesive which will adhere on contact, which satisfies the highest requirements concerning tack and quick stick, important especially in the use of self-adhesive tapes in fast-operating packing machinery, as well as concerning adhesive power on differing materials, including synthetic polymers, such as polyethylene and polyethyleneterephthalate, and which have self adhesive layers with exceptional properties adhering fast to the substrate, and which possess both high adhesive power and simultaneously good strength.

The process according to the invention for the manufacture of self-adhesive tapes or foils with an adhesive composition adhering on contact on the basis of copolymers of diesters of fumaric acid and vinyl compounds copolymerisable therewith is characterised in that an adhesive composition is taken on the basis of a copolymer which has been made by polymerisation of a monomer mixture of:

(A) 50-80 weight percent preferably 60-70 weight percent (taken on the total weight of the monomers) diesters of fnmaric acid with straight or branched chain saturated monovalent primary, secondary or tertiary aliphatic alcohols of 3 to 12 carbon atoms (B) 18-40% by weight, preferably 25-35% by weight (taken on the total weight of the monomers) of vinyl compounds copolymerisable with the diesters of fumaric acid, such as vinyl esters fo saturated aliphatic monocarboxylic acids, vinyl ethers, N-vinyl lactams, low acrylic or methacrylic acid esters or vinyl aromatic compounds,

as well as either (C) 0.5 to 15,% by weight, preferably 2-8% by weight, especially about 4 to 5% by weight (taken on the total weight of the monomers) of olefinically unsaturated copolymerisable polar compounds with carboxyl, carboxamide, dicarboxylic anhydride or dicarboximide groups, or

(D) 0.1 to 10% by weight, preferably 0.55% by weight, especially about 1% by weight (taken on the total weight of the monomers) of olefinically unsaturated copolymerisable compounds with self-crosslinking reactive groups, preferably those which contain hydroxy, epoxide, N-methylolamide, aldehyde or isocyanate groups,

or both components (C) and (D), wherein for each of components (A) to (D) one or more components can be used, wherein to the adhesive composition is added from 0.1 to 10% by weight, preferably 0.5 to by weight (taken on the copolymer) of a crosslinking active polyfunctional compound for copolymers of components (A), (B) and (C) and as required also for copolymers made using components (D), the adhesive is coated onto a substrate and finally subjected thereon to a short period heat treatment.

The copolymers according to the invention, which in the absence of solvents or thinners are tacky substances, can be used as self-cross-linkable adhesive compositions or as adhesive compositions crosslinkable by reactive additions. Thus, the invention also includes such copolymers of the composition given which attain the properties of good pressure-sensitive adhesive composition only after the resultant crosslinking on the substrate.

Suitable diesters of fumaric acid (component A) are, for example, di-isopropyl fumarate, di-n-butyl fumarate, di-sec-butyl fumarate, di-n-octyl fumarate, di-Z-ethylhexyl fumarate or di-dodecyl fumarate. These can be used either alone or in admixture with one another.

The vinyl esters of saturated aliphatic monocarboxylic acids (component B) can consist, for example, of vinyl acetate or vinyl butyrate, wherein both a single vinyl ester and a mixture of several vinyl esters can be used. The vinyl ester can be partly or wholly replaced, according to the quantity used and in dependence on the amounts of components C and/or D chosen, by other vinyl compounds copolymerisable with the fumaric acid diesters, such as vinyl ethers, e.g. vinyl isobutylether, N-vinyl lactans, e.g. N-vinylpyrrolidone, lower acrylic or methacrylic acid esters, e.g. methyl methacrylate, or vinylaromatic compounds, e.g. styrene. In this case, they can be used either singly or in admixture with one another, and, in the case of only partial replacement of the vinyl ester, must be copolymerisable therewith. By the term lower acrylic or methacrylic acid ester, there is meant especially esters of acrylic or methacrylic acid with monovalent aliphatic alcohols having 1 to 3 carbon atoms in the alcohol residue. For obtaining best results, lower acrylic or methacrylic acid esters and vinyl ethers should be present in an amount of at most by weight of the total weight of the monomers in the monomer mixture, while the remainder of component B then consists of vinyl esters, N-vinyl lactams should, as sole component in place of the vinyl ester, be present in the monomer mixture in an amount of at most 23% by weight on the total weight of the monomers; in connexion with a vinyl ester, about up to half the added amount of vinyl ester. In place of or together with the noted vinyl compounds, small quantities of other suitable unsaturated compounds can be copolymerised with the fumaric acid esters. The amount of the monomers of component B used to copolymerise with the monomers of component A is dependent on the type, the reactivity and the compatability of the monomers.

Copolymers, which are made only by copolymerisation of monomers of component A with monomers of component B, show even in the solventor thinner-free condition certain pressure-sensitive adhesive properties, but generally do not have the necessary inner strength. In order to achieve this it is necessary to copolymerise monomer mixtures which apart from components A and B contain up to by weight of component C, and/ or up to 10% by weight of component D, taken on the total weight of the monomers.

The polymerised-in polar groups of component C enable cross-linking reactions of such copolymers with other reactive groups in the copolymer itself or with reactive polyfunctional compounds added thereto, and also raise the adhesion onto polar surfaces.

The class of monomers with polar groups includes, for

example, monoesters of fumaric acid, maleic acid or itaconic acid with monovalent saturated aliphatic alcohols with l to 8 carbon atoms, and also crotonic acid, itaconic acid, methyleneglutaric acid, maleic acid anhydride or maleic acid imide, which likewise can be polymerised-in singly or in a mixture with one another.

In order to obtain self-crosslinking copolymers, the monomer mixture should contain such unsaturated copolymerisable monomers which, as well as the olefinic double bond, have one or more reactive groupings in the molecule (component D) which are thus able to react with the polar groups of the monomers of component C or with one another. Preferably as copolymerisable monomers of component D, compounds are used which contain hydroxy, epoxy, N-methylolamide, aldehyde or isocyanate groups. Examples of this type of monomer are: hydroxyalkyl esters or glycidyl esters of acrylic or methacrylic acid, N-methylolacrylamide, acrolein and isocyanatoalkylacrylates and methacrylates. These monomers also may be polymerised-in singly or in admixture. The quantity of the optionally useable monomers with reactive groups in the molecule (component C and/or (D) for copolymerisation with the monomers of components A and B is dependent upon the type and reactivity of the monomers, which in turn is dependent on the number of reactive groups in the molecule.

The crosslinking of the copolymer on the substrate can result either by self-crosslinking (combination ABD or ABCD)-if necessary with the aid of a crosslinking catalyst-or with the aid of a poly-functional compound added to the copolymer before coating onto the substrate, wherein in both cases temperatures between 50 and C. are to be maintained.

The manufacture of the pressure sensitive copolymers according to the invention can take place by the known methods of mass, solution or emulsion polymerisation, but is preferably carried out by dilution polymerisation. This dilution polymerisation is a variant of mass polymerisation in which the monomer mixture is first polymerised without the addition of solvents to a high viscosity and is then, if necessary several times, diluted. The copolymerisation is as usual carried out under a protective gas atmosphere and started with radical initiators, e.g. by using organic peroxides or azo compounds such as dibenzoyl peroxide, di-tert-butyl peroxide or u, a'-&ZO diiso-butyronitrile in mass, solution or dilution polymerisation, or water soluble initiators, such as potassium persulphate, in emulsion polymerisation. As well as this, further polymerisation aids such as control agents, chain transfer agents and, in the case of emulsion polymerisation, emulsifiers, protective colloids, buffering agents and thickening agents can be used. The K-value of Fikentscher (Cellulose-Chemie, 13 (1932), page 58) serves as a measure of the molecule size obtained by the copolymerisation. It is determined by measuring the viscosity of a 1% solution of the copolymer in a suitable organic solvent, e.g. toluene, at 20 C.

The K-value of copolymers according to the invention lie-according in each case to the polymerisation process and c0nditions-in the range 20 to 80, preferably about 30 to 70.

.Before bringing into the substrate, the copolymers or solutions, dispersions or emulsions thereof, can be mixed with additives, each according to its composition for further reaction (crosslinking) on the substrate. These additives can consist of a catalyst and/ or of one or more polyfunctional compounds.

As catalysts there may be used metal compounds, such as zinc chloride or acids, such as p-toluene sulphonic acid or octyl phosphoric acid, in amounts of up to about 1% taken on the copolymer. The catalyst can be addedas such or dissolved in water or an organic solvent to the copolymer.

As polyfunctional compounds, which are able to react with reactive groups of the copolymer, for example with carboxyl, hydroxyl, epoxy, N-methylolamide, aldehyde is isocyanate groups, for the process according to the invention compounds are preferably used which have two or more reactive epoxy or isocyanate groups in the molecule, or reactive thermosetting phenol resins. The amount to be used in each case depends on the type of polyfunctional compound chosen and must be matched in type and quantity to the reactive groups polymerised in the copolymer. It should not, however, generally exceed (taken on the copolymer or the solids content of the copolymer solution or dispersion). Catalysts can advantageously be employed when using polyfunctional compounds.

In order to obtain special efiects, there can further be added to the coating composition, in small quantity, adhesive resins, fillers, plasticisers, dyes or pigments. The use of plasticisers is especially to be recommended if the pro portions of component B lies at the upper limit of the range given, or if the adhesive tapes made using the copolymers of the invention are to be used at low temperatures.

The coating of the substrate with the copolymer or its solution, dispersion or emulsion can take place by normal coating devices on one or both sides, for example by doctoring, dip coating, trailing blade coating, bar coating or roller coating.

As substrates, there can be used foils of plastics or modified natural materials, paper, woven materials of all types, fleece materials, or fleecelike sheet fabrics, as well as metal foils, metallised plastics foils, asbestos and glass fibre cloths, foams or the like. If necessary, the substrate can be provided with an adhesion promoting interlayer.

The coated substrate is subjected to a short-period heat treatment to remove the solvent and to crosslink the copolymer, in which it is heated for up tolS minutes at a temperature between 50 and 150 C., preferably between 70 and 130 C. The period of the heat treatment may be shorter, the higher the temperature chosen.

The self-adhesive tapes or foils so obtained can after cooling be slit to the required width and put on the market rolled up into rolls. For facilitating unrolling, the rear side of the substrate may be provided with an antiadhesive coating or the adhesive side of the substrate may be provided with a covering material which is made adhesive repellent.

A further possible method of carrying out the process of the invention consists in coating the copolymer or a solution, dispersion or emulsion thereof onto a heated drum or endless steel belt, drying it on this intermediate carrier, partly or fully crosslinking it and then transferring it onto the substrate, such as, for example, fleece material or very porous paper, whereon the necessary full crosslinking of the copolymer in combination with the final substrate by means of a short heat impulse is carried out.

The advantages of copolymers of the present invention over other types of copolymers known for use for the same purpose, for example, those types on the basis of acrylic acid esters, consist, inter alia, in an easing of the manufacturing conditions and in an especially advantageous workability. The low polymerisation tendency of fumaratescompared with acrylates-facilitates the temperature control during polymerisation in the manufacture of the copolymers, so that for example in the use of fumarates as an essential component of the monomer mixture to be polymerized, a mass polymerisation without notable heat of reaction can be carried out. Compared to previously known pressure sensitive adhesive copolymers, important advantages also arise in the processing of the copolymers according to the invention in that, on account of their relatively low viscosity, it is possible to manufacture copolymer solutions or dispersions with a high solids content, and in the limiting case even solventfree pressure-sensitive adhesive copolymers, and to use these to coat substrates. From this, substantial savings in 6 solvent and acceleration of the drying process are obtained.

In this fashion, exceptional pressure sensitive adhesive tapes and foils are obtained, the adhesive layers of which possess all the characteristic properties of a good pressure sensitive adhesive. They are as follows:

(a) High contact tackiness (quickstic-k), which exceeds that of comparable pressure-sensitive adhesives on the basis of other copolymers, such as those of acrylic acid esters.

(b) High adhesive power to various materials, inter alia to metals, glass, paper, cloths, synthetic polymers of polar and non-polar type, eg on polyethylene and polyethylene terephthalate surfaces, wherein this adhesive power likewise exceeds that of the comparable acrylic acid ester copolymers.

(c) A good inner strength, suflicient for the most varied applications, even at high temperature, this cohesion of the pressure-sensitive adhesive layer being able to be increased for extreme specifications concerning hot strength by the addition of larger quantities of polyfunctional compounds or by further heat treatment at higher temperature.

Tackin'ess and adhesive power of pressure sensitive adhesive compositions according to the invention can be shown by the following test:

A foil is coated, for example a foil of polyethylene terephthalate, with a copolymer manufactured according to the invention, in such a way that after drying, a coating weight of only 12 gm./m. is obtained. A strip of the adhesive sheet so obtained is adhered under substantial pressure to a sheet of hard sized paper such as an index card. Directly thereafter, if one tries to pull the strip away again, the paper is split; with comparable pressure sensitive adhesive materials on the basis of other polymers or copolymers, e. g. those of acrylic acid esters, this effect is not obtained, and in those cases, the pressure sensitive adhesive material separates from the paper surface on pulling the strip away.

The following examples will serve to illustrate the invention:

EXAMPLE 1 Parts by weight Di-2-ethyl hexyl fumarate (A) 64.0 Vinyl acetate (B) 30.0 Monoisopropyl fumarate (C) 5.0 Glycidyl methacrylate (D) 1.0 Acetone 13.3 Petrol (boiling range 3085 C.) 53.4

In order to make the copolymer, the monomer mixture was placed in a vessel of glass or stainless steel which was provided with a stirrer, reflux condenser, thermometer and nitrogen feed (a gas inlet tube), and which could be beated in a waterbath, oilbath or steambath. The mixture of V monomers was dissolved in the mixture of acetone and benzene noted, and the mixture obtained saturated with nitrogen while stirring and warmed to the reflux temperature (48 C.). 0.2 part by Weight of dibenzoyl peroxide (75% in water) dissolved in a little acetone, were then added as initiator. The viscosity of the solution gradually increases during the continued refluxing. After 11, 13 and 14 hours reflux, calculated from the point of introduction of the initiator, the solution was diluted, each time with 35 parts by weight petrol of boiling range 60 to C. After a total reaction time of 15 hours, the solution had a copolymer content (solids content) of 34.6% by weight. The K-value of the so produced copolymer was 67.4, gbe asred on a 1% solution of the copolymer in toluene at For carrying out the K-value determination, the solution of the copolymer obtained as described was painted in a thin layer onto a paper strip provided with an antiadhesive coating (release paper), dried at room temperature and finally dissolved in the required quantity of toluene to give a 1% solution.

The viscous solution of the copolymer was coated, using a conventional coating apparatus, onto a polyethylene 8 adhesive power, but, for certain areas of use, insufficient holding power. By the addition of a small quantity of a triisocyanate as a polyfunctional compound to the solution of copolymer, a crosslinking during drying at 70 C. can

terephthalate foil .25 mm. thick. Thereafter, the coated take place after coating onto the substrate. For this, there foil was passed through a heated drying channel and was used as triisocyanate, the addition product of 3 mols dried for 5 minutes at high temperature to drive off the toluene diisocyanate with 1 mol of 1,1,1-trimethylolprosolvent. Thereby, a simultaneous self-crosslinking of the pane in the form of a 37.5% solution in ethyl acetate.

copolymer took place, as the values in the following table The quantities given in the following table are based on shows: this solution, calculated on the solids content Drying temperature, 0. Without With 1% With 2% crosslinktriisotrliso- 70 100 130 ing agent cyanate cyanate Coating weight, gmJm. 28. 4 28.1 28.1 Coating Weight (g./m. 22.1 25. 8 22.1

Adhesive power, gm. weight/cm 409 404 431 Adhesive power (gm. wt./cm.) 739 497 367 Holding power at. 50 C. (Inin.) 257 913 1,100 Holding power at 50 C. (min.) 3 245 336 Holding power at 100 0. (min) 12 33 1,128 Holding power at 100 C. (min.) 2 17 26 The values given in the table were determined after at If the same solution of the copolymer, mixed with 1% least 24 hours storage of the tapes or foils. 00 of the triisocyanate solution, was coated at greater thick- The coating weight was determined by weighing idenness onto a polyvinyl chloride foil of 0.2 mm. thickness tical sized pieces of uncoated and coated substrate mateand dried for 5 minutes at 70 C., the following values rial, and expressing the results in gm. per square metre. were measured:

For measuring the adhesive power, 10 to mm. wide 2 strips of the adhesive foil were adhered under light pres- 05 igiggi ggiy 3:6 i g /cm sure to sheets of polished and degreased stainless steel an Holding power f 'o' u 133 miniltes' rolled over to and fro with a weighted roller (2 cm. band- Holding power at 35 minutes width, speed 10 metres/minute) five times. The test strips were pulled away from the steel sheet in a tensile test EXAMPLE 3 machine and the values given by that given in grams 3O Parts y Welght weight per centimetre (pull off angle 180, pull off speed Df'z'ethylhexyl fumal'ate (A) 30 g n/minute). V y acetate For testing the heat resistance, or holding power, a Moho'z'ethylhexyl fumarate 5 X 3 by 1 thick Steel Plate was in the The monomer mixture was saturated with nitrogen 10118 direction With fy Paper cleaned Wlth hot without addition of solvents and warmed to 70 C., 0.1 Petrol and toluene- A Wlde adheslve tape about 15 part by weight benzoyl peroxide (75% in water) dissolved Wide was so adhered to the Pohshed and degreased in a little acetone, were added as initiator. The viscosity face of the steel plate, that taken from the edge of one of the reaction mixture rapidly After 1 and 1 Smaller Side, lehgth of y on the Steel P hours, taken from the time of adding the initiator, the The Stuck-0h Portion of the tape wasfheh Pressed on by 40 reaction mixture was diluted each time by 35 parts by one to and fro rolling with a 2 kg. weight roller. The free weight of petrol (boiling range After a total h of the sh'lp how hung up Vemcany and loaded reaction time of 15 hours, the solution of the copolymer Wlth an 300 welght thereon (400 The test has a solids content of 59.2% by weight. The K-value of was carried out at various temperatures (50 C. and 100 the copolymer amounted to 50.1 (measured in toluene at C.) and the time for falling off of the strip (and weight) measured mihutes- This solution of the copolymer was diluted further with As is evident from the table, the holding power rises petrol to a solids content of by weight and a Strongly Wlththe drylhg temperaturecycloaliphatic diepoxide (Union Carbide Corporations EXAMPLE 2 ERL-428?) was added in an amount of 5 to 8% taken on the SOIIdS content, and the solution then coated 1n con- Parts by wt. ventional fashion onto a polyethylene terephthalate foil Di..2.ethy1hexy1 f marat (A) 68.0 0.025 mm. thick, and dried in each case for 5 minutes Vinyl acetate (B) 30.0 at an elevated temperature of 100 and 130 C. Pressure 4-hydroxybutyl acrylate (D) -0 sensitive adhesive foils with the following properties were Acetone 13-3 obtained: Petrol (boiling range 30 to 85 C.) 53.4

To manufacture the copolymer, the monomer mixture 5% by weight 8% by weight was dissolved in the solvent mixture, as described in Exdlepoxide dlepoxide ample 1, and the resultant solution saturated with nitro- Drying temperature a O.) 100 130 m0 130 gen and warmed to reflux temperature (53 C.). 0.3 part C ht 2 1 y w i h f i ylpewxi e (1 i w diluted xiiihi...ajxhiztaa::::: 511 2-5; 2g; 1n a little acetone, were added as initiator. On continued gglg gg g0 X I lIilI-1)3:: 4, 01g gizggg 3,

warming at reflux temperature, the viscosity of the solution gradually increased. After 3 /2 and 6 /2 hours, starting from the addition of the initiator, the solution was diluted each time with 35 parts by weight of petrol (boiling range 60 to 95 C.). After a total reaction time of 11 hours, the solution so made of the copolymer had a solids content (polymer content) of 50.3% by weight. The K-value of the copolymer amounted to 39.9 (measured in toluene at 20 C.).

This solution of the copolymer was coated onto a 0.025 mm. thick foil of polyethylene terephthalate and dried for 5 minutes at 70 C. This pressure-senstiive adhesive foil showed in the dried uncrosslinked state an unusually high Coating weight g./m. 23.2 Adhesive power gm. wt./cm. 471 Holding power at 50 C. min. 1138 Holding power at C. min 1138 9 EXAMPLE 4 Parts by weight Di-Z-ethylhexyl fumarate (A) 71.0 Vinyl acetate (B) 25.0 Mono-n-butyl-maleinate (C) 4.0

The monomer mixture, without addition of solvents, was saturated with nitrogen and warmed to 78 C. 0.3 parts by weight of dibenzoyl peroxide (75% in water) diluted in a little acetone, were added as initiator. On continued heating of the reaction mixture at 78 C., the viscosity rapidly rose. After 2 /2, 4 and 14 /2 hours, taken from the time of adding the initiator, the mixture was each time diluted with 35 parts by weight of petrol (boiling range 60-95 C.). After a total reaction time of hours, the solution of copolymer had a solids content of (polymer content) of 46.1%. The K-value of the copolymer amounted to 47.1 (measured in toluene at C.).

This highly viscous solution was diluted further with petrol to a coatable consistency, provided at the same time with further additives and coated on the carrier material (see following table). As components mixed in there were used an epoxy resin (a cycloaliphatie diepoxide; Union Carbide Corporations ERI..-4289) as polyfunctional compound and zinc chloride as crosslin'king catalyst. The following values were measured.

After addition of 1.8 parts by weight of tetrabromomethane, the monomer mixture was saturated with nitrogen, brought to reaction temperature (about 65 C.) and treated with 6 parts by weight dibenzoyl peroxide (75% in water) as initiator. Polymerisation took place without noticeable heat of reaction. After 5 hours polymerisation at about 65 C., the reaction was interrupted. The copolymer still had a paintable consistency. The polymer content amounted to 83 to 88%, the K-value was at (measured in toluene at 20 C.).

The solvent free copolymer obtained was, after the addition of zinc chloride (in the form of a concentrated solution in ethyl acetate or isopropanol) coated onto a. 0.025 mm. thick polyethylene terephthalate foil and then crosslinked on the substrate by a subsequent heat treatment (5 minutes at 120 C.).

The following values relative to the pressure sensitive Adhesive Holding ppwer (min.)

Coating power weight (gm. wt./ Addition Carrier (g./m. Drying cm.) 50 0. 100C.

None Polyethylene terephthalate, 25-micron 30. 6 5 min., 70 C 537 11 3 10% diepoxide 0.5% ZnOlz do 28.0 5 min., 100 C..- 337 1, 276 1, 279 5% diepoxide 0.4% ZnCl2..-. Polyvinylebloride, 200mieron 55. 5 10 min., 79 C- 1, 360 28 l 13 7.5% diepoxid 2 ZnCl Kraft paper, 100 g./m. 26. 8 5 min., 100 C 300 90 90 Do Plastics coated cotton cloth 7 92. 5 .d0 207 8 4 D Hard polyvinyl-chloride, 100- 46. 3 5 min., 70 C 365 90 Do Aluminum foil, -micron 41.0 5 min., 100 C-.. 251 90 90 1 At 70 C 9 The coating took place using an aqueous plastics dispersion of a copolymer on the basis of an acrylic acid ester ("Acronal D", BASE).

Not measured.

The monomer mixture was dissolved in the mixture of petrol and acetone, the solution saturated with nitrogen and heated to reflux temperature C.). 0.3 part by weight dibenzoyl peroxide (75 in water) dissolved in a little acetone, were then added as initiator. During the continued heating the viscosity rose gradually. After 6, 8, 11 and 14% hours, taken from the introduction of the initiator, the solution was diluted each time with 35 parts by weight petrol (boiling range 60-95 C.). After a total reaction time of 15 hours, the solution had a solids content (polymer content) of 27.2%. The K-value of the copolymer amounted to 51.8 (measured in ethyl acetate at 20 C.).

The viscous solution of the copolymer was coated onto a foil of polyethylene terephthalate and dried for 5 minutes at 70 C. The so-manufactured pressure sensitive adhesive foil had in the uncrosslinked condition, an unusually high adhesive power. Its holding power at elevated temperature could be further improved by crosslinking with a triisocyanate (as in Example 2), as is evident from the following data:

adhesive properties were determined:

Zinc chloride (taken on The monomer mixture was dissolved in the mixture of petrol and acetone, the solution saturated with nitrogen and warmed to the reaction temperature (reflux temperature of the solution) (43 C.). 0.3 part by weight of dibenzoyl peroxide (75% in water) dissolved in a little acetone, were added as initiator. The viscosity of the solution slowly rose driving the polymerization process. After 16, 18 and 20 hours, taken from the time of addition of the initiator, the thickening solution was diluted with a total of parts by weight petrol (boiling range 60-95 C.). After a total reaction time of 22 hours, the solution had a polymer content of 42.3%. The K-value of the copolymer amounted to 51.9 (measured in toluene at 20 C.).

The viscous solution of the copolymer obtained was coated onto a polyethylene terephthalate foil and dried thereon for 5 minutes at 70 C. with simultaneous cross- 11 linking. After 24 hours storage of this pressure sensitive adhesive foil, the following values were measured:

Coating weight: 24.9 gm./rn. Adhesive power: 478 gm. wt./ cm. Holding power at 50 C.: 61 minutes Holding power at 100 C.: 12 minutes The monomer mixture was dissolved in the mixture of petrol and acetone, the solution saturated with nitrogen and heated to reaction temperature. (reflux temperature of the solvent mixture) (60 C.). 0.2 part by weight of dibenzoyl peroxide (75% in water) dissolved in a little acetone, were added as initiator. The viscosity of the solution slowly increased during the polymerisation process. After 10, 12 and 14 hours taken from the time of adding the initiator, the solution was diluted each time with 35 parts by weight of petrol (boiling range 60-95). After a total reaction time of 15 hours the resulting solution had a polymer content (solids content) of 32.2%. The K-value of the copolymer amounted to 47.5 (measured in toluene at C.).

The viscous solution of the copolymer obtained was coated onto a polyethylene terephthalate foil and subsequently dried for 5 minutes at 70 C. with simultaneous self-crosslinking. After 24 hours storage, the adhesive foil showed the following values:

Coating weight: 20.5 gm./m. Adhesive power: 358 gm. wt./cm. Holding power at 50 C.: 76 minutes. Holding power at 100 C.: 13 minutes.

The monomer mixture was saturated with nitrogen heated to about 70 C. and treated with 0.4 part by weight dibenzoyl peroxide (75% in water). The reaction proceeded without noticeable heat of reaction. Parallel with the increase of the viscosity, the reaction mixture was diluted during the polymerisation process, after 4 /2 hours taken from adding the initiator with 50 parts by weight ethyl acetate, after 6 hours with 50 parts by weight isopropanol and after 16 hours with 100 parts by weight petrol (boiling range 60-95 C.). Additionally, after about 6 hours, taken from the addition of the initiator, 0.6 part by weight of dibenzoyl peroxide (75 in water) were added. On expiry of about 22 hours, the polymerisation carried out at about 70 C. was interrupted.

The copolymer solution obtained had a solids content of about 50% the K-value of the copolymer amounted to 40 (measured in toluene at 20 C.).

The solution of copolymer was coated onto a foil of polyethylene terephthalate 0.025 mm. thick and dried for 5 minutes at 70 C. Parts of this solution were mixed with (a) 5% by weight kaolin and (b) 5% by weight titanium dioxide in order to obtain a white pigmented adhesive layer, and coated onto polyethylene terephthalate and dried as described above. The following values were obtained.

Mixture taken on solids content (copolymer content) 5% titanium None koalin dioxide Coating weight (gm/m3) 49. 7 59. 4 40. 1 Adhesive power (gm.wt./em.) 475 490 370 Holding power at 50 C. (min.) 23 14 32 Holding power at C. (min.) 6 3 3 EXAMPLE 1O Parts by weight Di-Z-ethylhexyl fumarate (A) 55 Di isopropyl fumarate (A) 10 Vinyl acetate (B) 30 Mono-isopropyl fumarate (C) 5 The monomer mixture was saturated with nitrogen, heated to 78 C. and reacted with 0.3 part by weight dibenzoyl peroxide (75% in water). The viscosity increased relatively rapidly. After 1 hour and '13 hours, taken from the time of adding the initiator, the mixture was diluted each time with 40 parts by weight acetone. After a total reaction time of 13 hours, the resulting copolymer solution had a solids content of 43.9%. The K-value of the copolymer amounted to 45.7 (measured in toluene at 20 C.).

The viscous solution was further diluted with acetone to a solids content of 40%, simultaneously mixed with 10% epoxy resin (ERL 4289) and coated onto a polyethylene terephthalate foil (25 microns). The following values were measured:

Monoisopropyl fumarate (C) 7.5 (5%) The monomer mixture was saturated with nitrogen, heated at 78 C. and reacted with 0.75 part by weight dibenzoyl peroxide (75% in water). After 12 hours, taken from the time of addition of the initiator, the solution was diluted with 40 parts by weight acetone, and half an hour later with parts by weight benzene (boiling range 60 to 95 C.). The polymer solution produced had a solids content of 48.5%. The K-value of the copolymer was 28.9, measured in toluene at 20 C.

The viscous solution was coated onto a 25 micron polyethylene terephthalate foil and dried at 70 C. for 5 minutes. At a coating weight of 29 gm./m. a high adhesive power was evident (610 gm. wt./cm.), but also an insufficient cohesion for some purposes. By mixing with 10% by weight epoxy resin (ERL-4289) and 1% by weight zinc chloride, the cohesion of the composition could be greatly increased.

The pressure sensitive adhesive with the just noted additions can be used with especial advantage for coating self-adhesive labels. A label paper (85 gm./m. was coated by a transfer process (Drying 5 minutes at C. on silicone paper and then transferred): the following values were measured:

coating weight 50.3 gmjm.

adhesive power: very highnot measureable since on pulling away, the paper split.

holding power at 50 C.: 31 minutes holding power at 100 C.: 6 minutes.

We claim as our invention:

1. A process for the manufacture of a pressure-sensitive adhesive material having an adhesive composition adhering on contact which comprises applying to a substrate a copolymer coating selected from the group con sisting of:

('1) a copolymer formed from the copolymerization of a monomer mixture of (A) 50-80% by weight, based on the total weight of the monomers, of at least one diester of fumaric acid and a saturated monovalent aliphatic alcohol containing from 3 to 12 carbon atoms,

(B) 18-40% by weight, based on the total weight of the monomers, of at least one vinyl compound copolymerizable with (A), and

(C) from 0.5 to 15% by weight, based on the total weight of the monomers, of at least one monoolefinic polar compound copolymerizable with (A) and (B) having a polar group selected from the class consisting of carboxyl, carboxamide, dicarboxylic acid anhydride and dicarboximide groups;

(2) a copolymer formed from the copolymerization of a monomer mixture of (A) 50-80% by weight, based on the total weight of the monomers, of at least one diester of fumaric acid and a saturated monovalent aliphatic alcohol containing from 3 to 12 carbon atoms,

(B) 18-40% by weight, based on the total weight of the monomers, of at least one vinyl compound copolymerizable with (A), and

(D) from 0.1 to by weight, based on the total weight of the monomers, of at least one monoolefinic compound copolymerizable with (A) and (B), said compound having self-crosslinkable reactive groups selected from the class consisting of hydroxy, epoxy, N methylolamide, aldehyde and isocyanate groups; and

(3) a copolymer formed from the copolymerization of a monomer mixture of (A) 50-80% by weight, based on the total weight of the monomers, of at least one diester of fumaric acid and a saturated monovalent aliphatic alcohol containing from 3 to 12 carbon atoms,

(B) 18-40% by weight, based on the total weight of the monomers, of at least one vinyl compound copolymerizable with (A),

'(C) from 0.5 to by weight, based on the total weight of the monomers, of at least one monoolefinic polar compound copolymerizable with (A) and (B) having a polar group selected from the class consisting of carboxyl, carboxamide, dicarboxylic acid anhydride and dicarboximide groups, and

(D) from 0.1 to 10% by weight, based on the total weight of the monomers, of at least one monoolefinic compound copolymerizable with (A), (B) and (C), said compound having self cross-linkable reactive groups selected from the class consisting of hydroxy, epoxy, N-methylolamide, aldehyde and isocyanate groups,

adding from 0.1 to 10% by weight of the copolymer of a cross-linking active polyfunctional compound for copolymers of the foregoing components, and subjecting the coating to a short heat treatment.

2. The process according to claim 1 wherein 'said copolymer coating is (1).

3. The process according to claim 1 wherein (A) is selected from the group consisting of di-isopropyl fumarate, di-n-butyl fumarate, di-sec-butyl fumarate, di-noctyl fumarate, di-Z-ethylhexyl fumarate and di-dodecyl fumarate.

4. The process according to claim 1 wherein (B) is selected from the group consisting of vinyl acetate, vinyl butyrate, vinyl lactams and mixtures thereof.

5. The process according to claim 1 wherein (B) is N-vinyl lactams in an amount of from 18-23% by weight, based on the total weight of the monomers.

6. The process according to claim 1 wherein (B) is a mixture of vinyl esters and N-vinyl lactams, said lactam being present in an amount of up to about onehalf the amount of the vinyl ester.

7. The process according to claim 1 wherein (C) is selected from the group consisting of monoesters of fumaric, maleic or itaconic acid with monovalent saturated aliphatic alcohols of from 1 to 8 carbon atoms, crotonic acid, itaconic acid, methyleneglutaric acid, maleic acid anhydride and maleic acid imide.

8. The process according to claim 1 wherein (D) is selected from the group consisting of hydroxyalkyl esters or glycidyl esters of acrylic or methacrylic acid, N-methylolacrylamide, acrolein, isocyanatoalkylacrylates and methacrylates.

9. The process according to claim 1, wherein:

(A) is selected from the group consisting of di-isopropyl fumarate, di-n-butyl fumarate, di-sec-butyl fumarate, di-n-octyl fumarate, di-2-ethylhexyl fumarate and di-dodecyl fumarate;

(B) is selected from the group consisting of (a) vinyl acetate, (b) vinyl butyrate, (c) N-vinyl lactams alone in an amount of from 18-23% by weight, based on the total weight of the monomers, and (d) a mixture of vinyl esters of N-vinyl lactams, said lactam being present in an amount of up to about one-half the amount of the vinyl ester;

'(C) is selected from the group consisting of monoesters of fumaric, maleic or itaconic acid with monovalent saturated aliphatic alcohols of from 1 to 8 carbon atoms, crotonic acid, itaconic acid, methyleneglutaric acid, maleic acid anhydride and maleic acid imide; and

(D) is selected from the group consisting of hydroxyalkyl esters or glycidyl esters of acrylic or methacrylic acid, N-methylolacrylamide, acrolein, isocyanatoalkylacrylates and methacrylates; and the cross-linking active polylfunctional compound is a triisocyanate or a cycloaliphatic diepoxide.

10. A process for the manufacture of a pressure-sensitive adhesive material having an adhesive composition adhering on contact which comprises applying to a substrate a copolymer coating selected from the group consisting of:

(1) a copolymer formed from the copolymerization of a monomer mixture of (A) 50-80% by weight, based on the total weight of the monomers, of at least one diester of fumaric acid and a saturated monovalent aliphatic alcohol containing from 3 to 12 carbon atoms,

(B) 18-40% by weight, based on the total weight of the monomers, of at least one vinyl compound copolymerizable with (A), and

(D) from 0.1 to 10% by weight, based on the total weight of the monomers, of at least one monoolefinic compound copolymerizable with (A) and (B), said compound having self crosslinkable reactive groups selected from the class consisting of hydroxy, epoxy, N-methylolamide, aldehyde and isocyanate groups; and

(2) a copolymer formed from the copolymerization of a monomer mixture of (A) 50-80% by weight, based on the total weight of the monomers, of at least one diester of fumaric acid and a saturated monovalent ali- 15 phatic alcohol containing from 3 to 12 carbon atoms,

(B) 18-40% by weight, based on the total weight of the monomers, of at least one vinyl compound copolymerizable with (A),

(C) from 0.5 to 15% by weight, based on the total weight of the monomers, of at least one monoolefinic polar compound copolymerizable with (A) and (B) having a polar group selected from the class consisting of carboxyl, carboxamide, dicarboxylic acid anhydride and dicarboximide groups, and

(D) from 0.1 to 10% by weight, based on the total weight of the monomers, of at least one monoolefinic compound copolymerizable with (A), (B) and (C), said compound having self cross-linkable reactive groups selected from the class consisting of hydroxy, epoxy, N-methylolamide, aldehyde and isocyanate groups,

and subjecting the coating to a short heat treatment.

11. The process according to claim 10, wherein:

(A) is selected from the group consisting of di-isopropyl fumarate, di-n-butyl fumarate, di-sec-butyl fumarate, di-n-octyl fumarate, di-Z-ethylhexyl fumarate and di-dodecyl fumarate;

(B) is selected from the group consisting of (a) vinyl acetate, (b) vinyl butyrate, (c) N-vinyl lactams alone in an amount of from 18-23% by weight, based on the total weight of the monomers, and (d) lactam being present in an amount of up to about one-half the amount of the vinyl ester;

(C) is selected from the group consisting of monoesters of furnaric, maleic or itaconic acid with monovalent saturated aliphatic alcohols of from 1 to 8 carbon atoms, crotonic acid, itaconic acid, methyleneglutaric acid, maleic acid anhydride and maleic acid imide; and

(D) is selected from the group consisting of hydroxyalkyl esters or glycidyl esters of acrylic or methacrylic acid, N-methylolacrylamide, acrolein, isocyanatoalkylacrylates and methacrylates.

References Cited UNITED STATES PATENTS 2,544,691 3/1951 Kugier et al. 117--122 UX 3,532,708 10/ 1970 Blance 26078.5 X 3,535,293 10/ 1970 Anderson 117-122 X 3,446,767 5/1969 Nolan 260-785 X 3,275,589 9/1966 Alexander et al. 117-161 X 2,544,692 3/ 1951 Kugler et al. 117-122 3,563,851 2/1971 Armour et al. 117161 X WILLIAM D. MARTIN, Primary Examiner B. D. PIANALTO, Assistant Examiner US. Cl. X.R.

11776 A, 68.5, 122 PF, 161 UT; 26077.5 CR, 78.5

a mixture of vinyl esters and N-vinyl lactams, said 30 B, 78.5 E, 78.5 T, 836, 844 

